How much of this do you need to do? If you are talking an enterprise-size solution (and the budget to back it up), a service like PrintUI.com (a former employer of mine) would be ideal, but it is way to expensive for a one-off situation.
An inexpensive, but complex, solution might be to create a PDF of the fixed elements, place that as a background, and allow your users to change the rest.
Your users would not be able to insert an image into a PDF form using Acrobat Reader.
Thanks for the info guys.
We were able to toss together a PDF from on top of one of our design documents using buttons to let users upload images and are actively looking into PrintUI.com as a possible long term more controlled solution.